FIG. 1 shows a basic structure of common photoelectric conversion devices such as thin film solar cells and the like. In the photoelectric conversion device, as shown in FIG. 1, a first electrode layer 2 composed of, for example, Mo to be a backside electrode is formed on a substrate 1 composed of, for example, soda-lime glass. Further, an optical absorption layer 3 composed of a compound semiconductor thin film is formed on the first electrode layer 2. Further, a transparent second electrode layer 5 composed of ZnO or the like is formed on the optical absorption layer 3 with a buffer layer 4 composed of ZnS, CdS or the like interposed therebetween.
As the optical absorption layer 3 composed of a compound semiconductor, a group-I-III-VI compound semiconductor thin film such as Cu(In,Ga)Se2, which can achieve high energy conversion efficiency, is employed.
Examples of a production method of Cu(In,Ga)Se2 include a production method in which a film is formed by applying a liquid phase raw material. As a production method of using such a liquid phase raw material, for example, a single source precursor method is heretofore known. This method is a production method of forming a Cu(In,Ga)Se2 thin film by allowing Cu, Se, and In or Ga to exist in one organic compound, dissolving the organic compound in an organic solvent, and applying and heat treating the resulting solution (U.S. Pat. No. 6,992,202).
However, in the production method using the above single source precursor, it is difficult to control the composition of the optical absorption layer, that is, a molar ratio (Cu/(In+Ga)), and there is a limitation of improvement in energy conversion efficiency. Therefore, further improvements in energy conversion efficiency of the photoelectric conversion device have been desired.
It is an object of the present invention to provide a photoelectric conversion device having high energy conversion efficiency by controlling composition of the optical absorption layer by use of the single source precursor.